Numerical Investigation on the Reference Crushing Stress of Granular Materials in Triaxial Compression Test

Abstract

KeywordsConstitutive model · particle crushing · single particle strength · particle diameter · relative density Yang WuDepartment of Civil Engineering, Yamaguchi University, Ube 7558611, Japan e-mail: yangwuuu0226@hotmail.com Haruyuki YamamotoGraduate School for International Development and Cooperation, Hiroshima University, Higashi-Hiroshima 7398529, Japan e-mail: a040564@hiroshima-u.ac.jp IntroductionEstimation of crushing stress is vital to comprehend the crushing mechanism of granular material. In geotechnical practice, it is significantly important to consider and decide the crushing stress of granular material when we estimate the bearing capacity of pile penetrating into crushable sand and analyze the stability of soil at bottom of the dam. For an individual particle, tensile strength is a very useful index because that it expresses the average stress or force on a single grain. It can be measured from a single particle crushing test. The volume of a grain is assumed to be spherical for simplification. Dexter and Kroesbergen (1985) [1] had compared a numbered of methods to calculate the tensile stress of granular materials. Many researchers (Jaeger (1967), McDowell et al. (1996), McDowell and Bolton (1998), Nakata et al. (2001b), McDowell and Debono (2013)) [2-6] had rewritten the equation by revising the expression of grain diameter. Essentially, the tensile stress expresses the strength of a grain from a micro viewpoint. In most cases, the crushing strength for a specimen of assembled grains but not an individual particle is in urgent demand for laboratorial tests and field practice. However, very limited studies have been conducted on the crushing stress of granular material in triaxial compression tests.The influence of such a kind of strength index on the mechanical behaviour of granular materials needs further examination. Harbin (1985) [7] had defined a relative breakage index containing the breakage reference stress. However, this breakage reference stress did not focus on its relevant form of granular material in triaxial tests from a macro viewpoint but was directly linked to the mechanical behaviour under specific loading. Nakata et al. (1999) [8] had only correlated the maximum value of mean normal stress with breakage factor. The constitutive model proposed by Yao et al. (2008) which adopts a reference crushing stress provides an option to solve this difficulty [9]. It is noted that no positive dilatancy of granular material in triaxial test occurs once the confining pressure exceeds a certain stress level. That stress is defined as the reference crushing stress. This constitutive model has been employed to evaluate the crushing

Coupled Effect of Carbon Nanotubes and Crushing on Shear Strength and Compression of Calcareous Sand Seeped by Colloidal Silica

“…So in the case of relatively low confining pressures of 100 kPa and 200 kPa, the volumetric strain first contracts then dilates, indicating that the crushing is relatively small, since such trend of volumetric-strain change is the typical case for noncrushable grains [32][33][34][35], or the typical case for few crushing of both noncemented breakable grains [36,37] and cemented breakable grains [38,39]. While as the confining pressure increases to 600 kPa, the specimen only exhibits contraction, indicating that crushing is dominant, as shown in the previous literature for non-cemented breakable grains [24,[40][41][42][43][44][45][46][47] Axial strain 𝜀 a (%) Deviatoric stress and cemented breakable grains [48]. So here we use the confining pressure as an indicator to approximately describe the degree of crushing.…”

Simple Modelling of Undrained Shear Response of Granular Materials

“…p cr refers to the mean stress when the peak stress ratio reduces to the stress ratio at the critical state. The peak stress ratio η p only emerges for the soil at the dense state [22][23][24]. η p approaches to η cr at the critical state as the mean stress p is increased to be identical to p cr .…”

Experimental Investigation on Crushing of Granular Material in One-Dimensional Test

“…22(b) demonstrate that some individual particles experience significant crushing and fracturing and produce a large amount of fines. In comparison with Toyoura sand, the volume of fine content for Masado is relatively larger because that the single particle strength of Masado is lower [13,39]. Masado is a typical sand composed of grains with different hardness.…”